Cannabis has been used for thousands of years, for a variety of medical, religious and recreational purposes (1) . Today it is used by 178 million people each year, or 3.8% of the global population (2). Despite its long history and abundance, it is difficult to think of many psychoactive substances that polarise opinion more than cannabis. Preparations of the plant Cannabis Sativa L. and the 100+ chemicals it produces (called ‘cannabinoids’, such as delta-9-tetrahydrocannabinol or ‘THC’) show potential in a wide range of applications in modern medicine. These include multiple sclerosis, chronic neuropathic pain, intractable nausea and vomiting, loss of appetite and weight in the context of cancer or AIDS, psychosis, epilepsy, addiction, and metabolic disorders (3) . Furthermore, when considering non-medical use, cannabis is often considered a ‘soft drug’; it is the only substance to have ever been reclassified to less harmful category in the UK Misuse of Drugs Act (this came into effect in 2004 but was reversed 5 years later). Nevertheless, strong concerns have been raised about the negative consequences of cannabis use (4, 5) . For example, it has been linked to an increased risk of psychotic disorders such as schizophrenia (6) . However, it is not clear whether cannabis actually increases this risk, or if it simply coincides with other factors that do, as explained elsewhere on the BAP website.
Another possible risk is addiction, which is estimated to affect 9% of people who try cannabis, 17% who start in adolescence, and 25-50% who use it daily (4) . As such, it is a far more common (but often underappreciated) risk compared to psychosis (7) . Addiction can be diagnosed as ‘Cannabis Use Disorder’ in medical terms, using the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). Cannabis Use Disorder can range from mild (2-3 items) to severe (6+ items) from the following symptoms:
- using cannabis in larger amounts or for longer than intended,
- a persistent desire, or inability, to cut down or control use,
- spending a great deal of time obtaining, using, or recovering from cannabis,
- craving, or a strong desire to use cannabis,
- failure to meet major life obligations because of cannabis
- continued use of cannabis despite social problems,
- giving up important activities because of cannabis,
- using it in hazardous situations,
- continued use despite physical or psychological problems related to cannabis,
- tolerance (needing more cannabis to get the same effect, or getting less effect when using the same amount),
- withdrawal symptoms when use is ceased, such as sleeping problems, anger and irritability.
Cannabis is becoming an increasing problem in addiction services. In the United Kingdom, the number of people entering specialist treatment for cannabis increased by 53% since 2005 (8, 9) . This is especially an issue for under 18’s, for whom 71% of addiction service admissions are now for cannabis compared to 20% for alcohol (9) . Although fewer people have been using cannabis in the last decade (10) , demand for cannabis treatment has risen alongside the prevalence of high potency cannabis (often called ‘skunk’) in the UK (11) . At the British Association for Psychopharmacology Summer Meeting in Bristol (July 2015) I will present data showing that high potency cannabis is more strongly linked to addiction than lower potency cannabis (such as hash or resin), and that younger people are especially vulnerable to its effects. Thus, the increasing availability of high potency cannabis may at least partly explain the rising incidence of cannabis addiction.
Psychological approaches to treat cannabis addiction are not very effective, and it is unclear which therapy is best (12) . There are no approved drug treatments, but a number have been tested (13) . Initial results suggest that gabapentin (used to treat seizures and pain) and N-Acetylcysteine (used to dissolve mucus and treat paracetamol overdose) show initial promise, although further evidence is needed (13) . Cannabis acts directly on the body’s natural (endogenous) cannabinoid system, which may become damaged after frequent use (14) . Preliminary evidence suggests that cannabidiol (a chemical produced by the cannabis plant, with some opposing effects to THC) may have potential for treating addiction (15, 16) . Our team at the Clinical Psychopharmacology Unit are now testing whether cannabidiol can help people with cannabis addiction in a controlled clinical trial.
Cannabis addiction is an increasingly prevalent concern, especially among young people. A safe and effective treatment could be hugely beneficial for offsetting possible mental and physical health issues related to cannabis and improving educational and work attainment. Whilst it is important that clinicians and users alike recognise that cannabis addiction is a genuine risk, it is also crucial to remember that it only affects a minority of users, and many people will enjoy the effects of cannabis without suffering adverse consequences.
- Murray RM, Morrison PD, Henquet C, Di Forti M. Cannabis, the mind and society: the hash realities. Nature Reviews Neuroscience. 2007;8(11):885-95.
- United Nations Office on Drugs and Crime, World Drug Report 2014 (United Nations publication, Sales No. E.14.XI.7).
- Robson P. Therapeutic potential of cannabinoid medicines. Drug testing and analysis. 2014;6(1-2):24-30.
- Volkow ND, Baler RD, Compton WM, Weiss SR. Adverse health effects of marijuana use. N Engl J Med. 2014;370(23):2219-27.
- Hall W. What has research over the past two decades revealed about the adverse health effects of recreational cannabis use? Addiction. 2015;110(1):19-35.
- Moore TH, Zammit S, Lingford-Hughes A, Barnes TR, Jones PB, Burke M, et al. Cannabis use and risk of psychotic or affective mental health outcomes: a systematic review. The Lancet. 2007;370(9584):319-28.
- Hall W, & Degenhardt, L. . High Potency Cannabis. BMJ. 2015;350:h1205.
- NDTMS. Adult Drug Statistics from the National Drug Treatment Monitoring System (NDTMS). Public Health England. 2014.
- NDTMS. Young people’s statistics from the National Drug Treatment Monitoring System (NDTMS). Public Health England. 2015.
- Home Office (2014). Drug Misuse: Findings from the 2013 to 2014 Crime Survey For England and Wales.
- Hardwick S, King LA. Home Office cannabis potency study 2008: Home Office Scientific Development Branch United Kingdom; 2008.
- Denis C, Lavie E, Fatseas M, Auriacombe M. Psychotherapeutic interventions for cannabis abuse and/or dependence in outpatient settings. The Cochrane Library. 2006.
- Marshall K GL, Ali R, Le Foll B. Pharmacotherapies for cannabis dependence. Cochrane Database of Systematic Reviews. 2014(12):CD008940.
- Morgan CJ, Page E, Schaefer C, Chatten K, Manocha A, Gulati S, et al. Cerebrospinal fluid anandamide levels, cannabis use and psychotic-like symptoms. The British Journal of Psychiatry. 2013;202(5):381-2.
- Morgan CJ, Freeman TP, Schafer GL, Curran HV. Cannabidiol attenuates the appetitive effects of Δ9-tetrahydrocannabinol in humans smoking their chosen cannabis. Neuropsychopharmacology. 2010;35(9):1879-85.
- Morgan CJ, Das RK, Joye A, Curran HV, Kamboj SK. Cannabidiol reduces cigarette consumption in tobacco smokers: Preliminary findings. Addict Behav. 2013;38(9):2433-6.